Adverse responses to protamine sulfate have been known for many years. Previous exposure to protamine can induce a humoral immune response and predispose susceptible individuals to the development of untoward reactions from the subsequent use of this drug. Patients exposed to protamine through the use of protamine-containing insulin or during heparin neutralization may experience life-threatening reactions and fatal anaphylaxis upon receiving large doses of protamine intravenously. Severe reactions to intravenous protamine can occur in the absence of local or systemic allergic reactions to subcutaneous injection of protamine-containing insulin. Although there is no clear evidence for hypersensitivity reactions of protamine sulphate linked to vaccination, vaccines containing protamine impurities have a precaution and contraindication warning in their labels stating that a serious allergic reaction after a previous dose of such a protamine containing vaccine (e.g. IXIARO®, see CDC site http://www.cdc.gov/japaneseencephalitis/vaccine/) is a contraindication to further doses. Thus elimination of said impurity is a medical request for an improved safety profile. On the other hand protamine sulphate is an excellent tool (and often better than other reagents such as benzonase) to purify crude harvests of viruses grown on cell substrates.
Chikungunya virus (ChikV) is a positive-sense, single-stranded RNA virus from the genus Alphavirus, family Togaviridae. Chikungunya virus disease is mainly an outbreak disease and is associated with high attack rates. The virus is transmitted to humans via a mosquito vector and causes fever, rash, fatigue and severe polyarthralgia. Infections with ChikV generally resolve spontaneously and are not usually fatal, except in rare cases involving CNS infection, where the death rate is from 10-30%. Particularly at risk for ChikV CNS disease are infants under one year and adults over 65 years, with an infection rate of 25-fold and 6-fold higher than the general population, respectively, and with a rate of persistent disabilities estimated at between 30% and 45% (Gerardin, 2016). Furthermore, about 30 percent of all ChikV patients experience arthralgia for months to years after recovery. In some cases, neurological, renal, cardiac, respiratory or hepatic complications can also result.
There are currently no vaccines or medications available for the treatment or prevention of Chikungunya virus disease. Outbreaks in the past have occurred mainly in Africa, but the Central/East/South African (ECSA) genotype has recently expanded its geographical range, resulting in outbreaks in India, Asia, and even temperate Europe (Weaver, S., Arrival of Chikungunya Virus in the New World: Prospects for Spread and Impact on Public Health PLOS Neglected Tropical Diseases (2014) 8(6): e2921). Although ChikV has been repeatedly imported into the Americas since 1995, no autochthonous transmission was reported until 2013 in the Caribbean. By 2015, the epidemic had spread to the mainland and caused more than 1,000,000 suspected cases in 43 countries in the Americas (Pan-American Health Organization (2015) Number of Cumulative Cases of Chikungunya Fever in the Americas). Further epidemics may been aided in part by the spread of the ChikV mosquito vector into non-endemic regions, as well as the ability of ChikV to adapt to local mosquito species (Vega-Rua et al., Chikungunya Virus Transmission Potential by Local Aedes Mosquitoes in the Americas and Europe, May 20, 2015, PLOS Neglected Tropical Diseases DOI:10.1371/journal.pntd.0003780). The high rate of contagion of Chikungunya virus disease, its potential for long-lasting complications, as well as its geographical spread underscore the need for developing preventative measures, such as vaccines.
In 2007, Zika virus was detected for the first time outside of the endemic regions of Asia and Africa since its discovery in a Rhesus monkey in Uganda in 1947. Since then, the virus has caused a large epidemic in French Polynesia, spreading through islands in the Pacific and into South and Central America by 2015 (WHO “Zika Situation Report” Feb. 5, 2016). Evidence suggests that in addition to being transmitted by Aedes species mosquitoes, other vectors may exist, and the virus may be transmitted by blood transfusion, transplacentally, and through sexual transmission (WHO Zika Virus Fact Sheet, February 2016). Though the symptoms of Zika virus infection include mild fever, rash, and conjunctivitis, there is a likely correlation between infection and neurological disorders, including Guillain-Barré syndrome and microcephaly in fetuses/neonates subsequent to infection during pregnancy. There is currently no specific treatment or vaccine for Zika virus and the only preventative measures involve control of the mosquito vector. Zika virus presents a substantial public health threat due to the wide circulation of the Aedes mosquito, multiple routes of transmission, and potentially severe neurological effects of infection.
Yellow fever (YF) still represents a constant threat to public health in endemic regions of tropical Africa and South America. The World Health Organization (WHO) estimated that 200,000 cases occur annually with 30,000 fatalities (WHO 2009). Yellow fever virus (YFV), a single-stranded RNA virus, belongs to the family of the Flaviviridae and is transmitted by mosquitoes (Lindenbach B D, Thiel H J, and Rice C M 2007). Yellow fever disease can be divided into three stages. After an incubation period of three to six days, patients develop febrile illness with symptoms like fever, malaise, lower back pain, headache, myalgia, nausea, vomiting, and prostration lasting three to four days. Symptoms disappear for two to forty-eight hours before fifteen to twenty-five percent of the patients enter the third phase, the period of intoxication, characterized by fever, vomiting, epigastric pain, hemorrhagic diathesis, jaundice, and liver and renal failure. Death occurs in twenty to fifty percent of severe YF cases on the seventh to tenth day (Monath 2001; Monath 2004; Gubler, Kuno, and Markoff 2007).